1. Field of the Invention
The present invention relates to a pattern drawing device for forming minute patterns on thin films such as those formed on substrates during the process of manufacturing integrated circuits, display devices, optical devices and other such devices.
2. Description of the Related Art
Thin film patterning steps are essential in the manufacture semiconductor substrates, optical devices and other such devices. Patterning, for example, is performed by applying a photo resist layer on the thin film to be processed, exposing a pattern on such photo resist, developing the exposed photo resist to form a resist pattern, and etching thin film using the resist pattern as an etch mask. A pattern drawing device is used for exposing the pattern on the photo resist, typically through the use of a photo mask or utilizing an exposure method employing an optical beam scanning technique. The latter is used in the preparation of an optical disk original and drawing of free patterns. For instance, Japanese Patent Laid-Open Publication No. S59-171119 and Japanese Patent Laid Open Publication No. H10-11814 describe a pattern drawing device employing a rotational scanning system. These pattern drawing devices mount a substrate coated with photo resist on a turntable, and draw patterns on the substrate by performing rotational scanning with a laser beam modulated with pattern data.
Nevertheless, with the aforementioned pattern drawing devices employing the rotational scanning system, the original pattern data read by the X-Y coordinate system with a device such as a scanner and saved as a stored pattern is converted into an r-θ coordinate system, and this r-θ pixel data is temporarily stored in the memory. The pixel data is then read from the memory in synchronization with the substrate rotation and used to modulate the optical beam so as to draw a pattern by selectively exposing the photo resist. Thus, data for the r-θ coordinate system must be converted each time the stored pattern to be drawn is rotationally scanned at least once (1 track worth). When it is necessary to draw a high-resolution pattern, because data must be converted from an X-Y coordinate system to the r-θ coordinate system for all drawing points on the circumference of each track, the operational load increases, and the conversion time expands, thereby restricting high-speed drawing. Moreover, when the processing performance of the CPU is relatively low, drawing of high-resolution or multi-valued patterns is restricted and a larger CPU capacity and/or larger memory will be required for adequate performance.